EP0321509A1

EP0321509A1 - Automatic transmission

Info

Publication number: EP0321509A1
Application number: EP88904678A
Authority: EP
Inventors: Arne Austad
Original assignee: AUTOSHIFT AS
Current assignee: AUTOSHIFT AS
Priority date: 1987-05-27
Filing date: 1988-05-27
Publication date: 1989-06-28
Also published as: FI890383A0; NO162165B; JPH02500767A; FI890383A; WO1988009450A1; AU1784488A; NO162165C; NO872225L; NO872225D0

Abstract

La présente invention se rapporte à une transmission automatique (15) qui change de vitesse uniquement en fonction du couple qui s'excerce sur l'arbre d'entrée (10) et sur l'arbre de sortie (11), lesquels sont reliés en permanence par des roues d'entraînement (1, 2, 3, 4). L'arbre d'entrée (10) comporte une partie ayant des filetages externes (9) sur laquelle est disposée une première roue d'entraînement (1) présentant des filetages internes complémentaires, de sorte que la première roue d'entraînement soit légèrement mobile dans le sens axial par rapport à l'arbre d'entrée (10). Une deuxième roue d'entraînement (2) peut se déplacer axiallement et tourner librement sur l'arbre d'entrée (10) de façon à se placer en prise, tel un organe d'accouplement (17), avec une roue en anneau (8) qui est fixée à l'arbre d'entrée. Une troisième roue d'entraînement à engrenage libre (3) repose sur l'arbre de sortie (11) et s'engrène en permanence avec la première roue d'entraînement (1). Une quatrième roue d'entraînement (4) est fixée à l'arbre de sortie (11) et s'engrène en permanence avec la deuxième roue d'entraînement (2). Un organe tel qu'un ressort (7) sollicite la première roue d'entraînement (1) dans un sens axial en direction de la deuxième roue d'entraînement (2), en vue de se placer en prise avec elle.The present invention relates to an automatic transmission (15) which changes speed only as a function of the torque exerted on the input shaft (10) and on the output shaft (11), which are connected in permanently by drive wheels (1, 2, 3, 4). The input shaft (10) has a part having external threads (9) on which is disposed a first drive wheel (1) having complementary internal threads, so that the first drive wheel is slightly movable in the axial direction with respect to the input shaft (10). A second drive wheel (2) can move axially and freely rotate on the input shaft (10) so as to engage, like a coupling member (17), with a ring wheel ( 8) which is attached to the input shaft. A third freewheel drive wheel (3) rests on the output shaft (11) and permanently meshes with the first drive wheel (1). A fourth drive wheel (4) is attached to the output shaft (11) and permanently meshes with the second drive wheel (2). A member such as a spring (7) biases the first drive wheel (1) in an axial direction in the direction of the second drive wheel (2), in order to engage with it.

Description

AUTOMATIC TRANSMISSION

The present invention relates to an automatic transmission which will shift only dependent on the torque in the input shaft and the output shaft with said shafts always being interconnected via drive wheel means.

Automatic transmissions are well known and are, inter alia, used in various vehicles. Transmissions with several gear rations are also used for other purposes, e.g. winches, capstans, and various machines used in forestry and agri¬ culture.

Automatic transmissions are known and widely used in private cars, trucks and motor coaches, etc. In addition to a fluid torque converter and a transmission, is a hydraulic system for controlling and activating various transmission functions included. In order to achieve smooth shifting operation such transmissions are operated by dependence on the speed of rotation of one transmission shaft as well as throttle opening. Automatic V-belt transmissions with variable pulleys are also known.

By the automatic transmission according to the invention is a simple construction achieved, the structure of which is much similar to that of conventional manual standard transmiss¬ ions. By the present concept is a higher shifting level from high to low than from low to high achieved, which entails that the high gear is engaged as long as possible and the low gear is engaged not more than strictly necessary. The present concept also has the pre-eminence that the shifting level may be set or adjusted by the user.

According to the invention this is achieved by the fact that the input shaft comprises a portion provided with external thread means on which a first driving wheel means having complementary internal thread means is running in such a way that said first driving wheel means is slightly axially moveable in relation to said input shaft along said threaded portions, and that a second axially sliding and freely rotatable driving wheel means is mounted on the input shaft for releasable engaging a ring wheel fixed to said input sha t as a coupling means, and that a third free wheeled driving wheel is supported on said output shaft, said third driving wheel means being constantly in mesh with said first driving wheel means, and that a fourth driving wheel means is fixed to the output shaft and is constantly in mesh with said second driving wheel means, and means urging said first driving wheel means axially towards and into engagement with said second driving wheel means.

Further embodiments and further features of the present invention will appear from the following dependent claims.

Further objects, features and advantages of the invention will appear from the following disclosure of embodiments of the Invention presently preferred and disclosed by way of an example with reference to the drawings, where

Fig. 1 is a diagrammatical view of a first embodiment of the transmission according to the invention, Fig. 2 is a diagrammatical view of two transmissions which are connected in series in order to increase the number of gear ratios, Fig. 3 is a diagrammatical view of a second embodiment of the transmission according to the invention, Fig. 4 is a diagrammatical view of a variant of the second embodiment of the invention, Fig. 5 is a diagrammatical view of another variant of the second embodiment according to the invention, Fig. 6 is a diagrammatical view of a third embodiment of the present invention, Fig. 7 is a diagrammatical view of the first embodiment of the transmission according to the invention in a high gear, Fig. 8 is a diagrammatical view of the first embodiment of the transmission according to the invention in a low gear, and Fig. 9 is a torque diagram of the shift between high and low, and between low and high.

Reference is made to fig. 1 which is a diagrammatical view of an automatic transmission 15 having two shifting steps (two-speed). An input shaft 10 is supported in a surrounding case 5, and similarly is an output shaft 11 supported in the case 5. The shaft 10 has an externally threaded portion 9 preferably of a steep pitch angle, e.g. of the kind used in Bendix-drives. A first gear 1 having complementary internal threads is mounted on said shaft portion and is slightly axially moveable along the threaded sections. The gear 1 has external teeth which may be straight cut, but are preferably helical gears. A spring 7, preferably a coil spring, is provided between the gear 1 and a spring seat 6. The seat or disc 6 has internal threads cooperating with corresponding threads on the shaft 10. The spring 7 can be tensioned and relieved, respectively, by turning the disc 6. A second sliding gear 2 is mounted on input shaft 10 and thus is able to slight movements in an axial direction. The gear 2 is also freely rotatable on shaft 10. A ring wheel 8 is fixedly connected to input shaft 10. The illustrated clearances between the first gear 1 and the second gear 2, and between the second gear 2 and the ring wheel 8 are in fact very small in a true construction. The first gear 1 is meshed with a third gear 3 which is supported on output shaft 11 via a sprag or free wheel clutch means 13. The free wheel 13 causes the third gear 3 to turn freely in one direction relative to the shaft 11, and locks to the shaft upon rotation in the opposite direction. A fourth gear 4 is fixed to the output shaft 11 and is meshed with the second gear 2. The pairs of gears 1 and 3, and 2 and 4, respectively, are always mutually engaged, but as mentioned the gears 1 and 2 is able to move slightly along the shaft 10 and thus along the gears 3 and 4. The gear set 1 and 3 forms a low gear, whereas the gear set 2 and 4 forms a high gear.

In^'fig. 2-8 components corresponding to those shown in fig. 1 are designated by the same reference numbers. Fig. 2 is a diagrammatical view of an automatic multistep transmission with two equal transmission units 15 and 15' connected In series. The transmissions 15 and 15' are constructed as disclosed with respect to fig. 1. Such an interconnection will provide a four-step transmission. Various shift levels will be determined by dimensioning of the couplings or clutches, the gears and by adjustment of the springs.

Fig. 3 presents a second embodiment of the automatic transmission 25 according to the invention. The input shaft 10 with associated components is constructed- similar to the input shaft shown in fig. 1, except for the first gear 1. In the embodiment the gear 1 is designed as a free wheel via a sprag or one-way clutch 13 preventing rotation of the gear in relation to the shaft 10 in one particular direction. As in the first embodiment the shaft is provided with a threaded portion 9, and the gear 1 has corresponding internal threads. In the embodiment, however, is the output shaft constituded of a surrounding drum 21 provided with internal gears 23, 24 which mesh with the gear 1 and the gear 2, respectively. The drum 21 is rotatable in fixed bearings 18 and 18'. The input shaft 10 is in turn eccentrically supported in the fixed bearings 18 and 18'.

Fig. 4 presents a third embodiment 35 of the automatic transmission according to the invention. The input shaft 10 corresponds to the input shaft in fig. 3 as regards structure and function. In similarity to fig. 3 this embodiment also comprises a surrounding drum 31 with internal gears 33 and 34. In this embodiment, however, intermediate or planetary gears 38 and 39 are provided between the gears 1 and 33 and the gears 2 and 34, respectively. By means of the planetary gears 38 and 39 reversal of the direction of rotation is achieved for the output shaft or drum 31. Similar to fig. 3 the drum 31 is supported in stationary bearings 18 and 18'. Fig. 5 presents an automatic transmission which is a variant of the embodiment shown in fig. 4. The input shaft 10 with associated components is similarly constructed to the shaft shown in fig. 4. However, the input shaft 10 is centric supported in the bearings 19 and 19'. The surrounding drum 41 with associated internal gears 43 and 44 corresponds substantially to the drum 31 in fig. 4. The planetary gears 48 and 49 are slightly larger than the gears 38 and 39, and the gear ratio achieved is thus altered.

Fig. 6 presents a fourth embodiment Of the automatic transmission 55 according to the invention. As in previously disclosed embodiments the input shaft 10 is -provided with a spring seat or disc 6 and a first gear 1 and an intermediate spring 7 therebetween. As in the embodiments according to fig. 3 and 4 the input shaft 10 is eccentrically supported in bearings 18 and 18'. The gear 1 is - as shown in fig. 3,4 and 5 - engaged to the shaft 10 via threads 9 and free wheel clutch means or sprag 13. The gear 1 is meshed with the gear 58 which is fixedly connected to a shaft 56 which is, in turn, fixedly connected to a smaller gear 59. On the input shaft 10 a multiple lamella clutch 52 is also provided with one set of lamellas or discs engaged to the input shaft 10. The other set of discs is engaged to a ring gear 57 which is provided with external teeth engaged with the gear 59. Said ring gear 57 is also engaged with a gear 54 internal of the drum 51. By a transmission of this kind with transition gears a considerably higher gear ratio is achieved. The ring gear 57 will act to transmit the torque both in high and low gear. Fig. 7 presents a more structural embodiment of the automatic transmission 15 according to the invention. It is shown more clearly how the coupling between the second gear 2 and the ring wheel 8 may be effected. This preferred embodiment comprises an internal cone or taper in the ring wheel 8 and an external cone provided on the second gear 2. Together said components form a conical coupling or clutch 17. As indicated in the fig. , the first gear 1 is also able to thrust on the second gear 2. As shown, both first and second gears can move slightly in an axial direction in relation to the input shaft 10. Fig. 7 shows the conical coupling 17 in an engaged position causing power to be transmitted via the gears 2 and 4, I.e. in high gear.

Fig. 8 presents a transmission 15 corresponding to that in fig. 7, except the power being transmitted via the gear set 1 and 3, i.e. in low gear.

Fig. 9 presents a torque diagram indicating that shifting from low to high gear will occur at a lower torque than shifting from high to low. This fact will be further described below.

In order to better understand the operation of the transmiss¬ ion a more comprehensible description of the automatic transmission will be given with reference to fig. 7, but may readily be understood In connection with the other embodi¬ ments. Normally, the power will be transmitted via the gear set 2 and 4, i.e. in high gear. This occurs since the spring 7, which is at one end in contact with the adjustable disc 6, thrusts against the first gear 1 with its other end. The gear 1 is slightly axially moveable along the threaded portion 9, which will, naturally, cause the gear 1 to turn slightly simoultaneously as it is axially displaced. As mentioned, the spring 7 presses against the gear 1 which is, in turn, pressed towards the second gear 2, which is also axially slidably and freely rotatable supported on the input shaft 10. The ring wheel 8 is fixed to the shaft 10, and by means of the spring 7 the second gear 2 is forced into conical engagement with the ring wheel 8 so as to be locked to the ring wheel 8. Power is transmitted from the gear 2 to the gear 4 which is fixed to the output shaft 11. The first gear 1, however, will have the same rotational speed as the second gear 2. In order to avoid locking the third gear 3 is mounted on the shaft 11 via the one way clutch or sprag 13, so that the gear 3 runs like a free wheel on the shaft 11. Thus the gear 3 will rotate at a lower speed than the output shaft 11. In case of increased torque demand the torque transferable through the conical coupling 17 will be exceeded at a certain value. At this limit value the coupling 17 will momentarily slip. The rotational speed of the output shaft 11 will immediately be reduced to correspond with the rotational speed of gear wheel 3. Then the sprag accellerating will lock the gear 3 to the output shaft 11. Since the gear 1 is mounted on the input shaft via a threaded portion, preferably of the Bendix-drive type, the gear 1 will when loaded be screwed to the right hand side in the fig. and consequently against the spring force. In this way the coupling 17 is completely released, and the gear 2 is able to run freely on the shaft 10. The gears 3 and 4 will then rotate with the same rotational speed as the output shaft 11, but no power is transmitted through the gears 4 and 2, as the gear 2 is disengaged. The gear 3 is only able to stand still or rotate in the opposite direction relative to the output shaft.

When the torque demand again decreases the spring 7 will at a certain torque value push the gears 1 and 2 to the left hand side in the fig., i.e. the coupling 17 will reengage. The gear 2 is reconnected to the input shaft 10 via the ring wheel 8. The rotational speed of the output shaft 11 increases since the power is transmitted via the gear set 2 and 4. No power is transmitted to the gear 3 since the output shaft 11 rotates at a higher speed than the gear 3. The shifting torque is controlled by the spring 7. The transmittable torque is proportional to the spring pressure against the coupling. The spring pressure and, thus, the transmittable torque can be adjusted by means of the disc 6, as previously stated. In shifting from high gear to low gear only the transmittable torque via the coupling is decisive. If the gears are helical as in fig. 7 a power component will be created towards the right hand side in the fig. , or against the spring force when driving in low gear. In low gear operation the gear 1 is further screwed towards the right hand side in the fig. by means of its internal threads. This force also acts against the spring force. As will appear from the torque diagram in fig. 9 shifting from low gear will, thus, occur at a lower torque than shifting from high to low.

The other embodiments, except the one shown in fig. 6, operates correspondingly, but the gears and shafts are designed and located in a different way. The mode of operation of the automatic transmission 55 as shown in fig. 6 is as follows: In high gear the first gear 1 Is forced towards the coupling 52 by means of the spring 7. The power is transmitted to the ring gear 57 which is meshed with the internal gear 54 in the drum 51. Rotational movement is also transmitted from the ring gear 57 to the transfer gear 59, and further to the intermediate gear 58. The intermediate gear 58 is in turn in mesh with the gear 1 which runs like a free wheel by means of the sprag or clutch 13. In this case (also according to fig. 3,4 and 5), the sprag runs on an externally smooth sleeve (not detailed in the drawings) internally provided with the helical threads, which sprag and sleeve are axially retained to the gear 1. At increased torque demand the transferable torque via the coupling 52 will be exceeded at a certain value. At this limit value the coupling 52 will momentarily slip. The rotational speed of the output shaft or drum 51 will immediately be reduced or converged towards the gear 1 until engagement with the shaft 10. The power is now transmitted by the gear 1, the inter¬ mediate gear 58 via the shaft 56 and to the gear 59 and, further, via the ring gear 57 to the internal gear 54 in the drum 51. Consequently is a transmission with considerably higher shift ratio between high and low gear achieved.

It will be appreciated that the coupling 17 not necessarily need to be of the conical or tapered kind, but may be of any

10 suitable kind, e.g. of the multi-disc kind. It is also to be understood that the driving wheels means not necessarily are gears, but may be belt pulleys, frictional rollers or any kind of means able to transmit torques or power. Similarly the spring pressing against the first driving wheel means may t5 be any means providing a thrust or bias, e.g. a Belleville spring, hydraulically regulatable pressure, or the like. The transmission may be of the type running in an oil bath, or it may be a dry type transmission using plastic and teflon components. 0

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Claims

CLAIMS:

1.

An automatic transmission which only shifts dependent on the torque in the input shaft and the output shaft, which shafts always being interconnected via drive wheel means, c h a r a c t e r i z e d i n that said input shaft (10) includes a portion provided with, external thread means (9) on which a first driving wheel means (1) having complementary internal thread means is mounted in such a way that said _t0 first driving wheel means is slightly axially moveable relative to said input shaft (10) along said threaded portions, and that a second axially moveable and freely rotatable driving wheel means (2) is mounted on said input shaft (10) for releasably engaging as a coupling means (17)

₁₅ the ring wheel (8) fixed to said input shaft (10), and that a third free wheeled driving wheel means (3) is supported on said output shaft (11), said third driving wheel means being constantly in mesh with said first driving wheel means (1), and that a fourth driving wheel means (4) is fixed to said

₂₀ output shaft (11) and is constantly in mesh with said second driving wheel means (2), and means (7) pre-ssing said first driving wheel means (1) axially towards and into engagement with said second driving wheel means (2).

25 ^^*

An automatic transmission which only shifts dependent on the torque in the input shaft, which shafts always being interconnected via drive wheel means, c h a r a c t e r i z e d i n that said input shaft (10)

₃₀ includes a portion provided with external thread means (9) on which a first driving wheel means (1) having complementary internal thread means is mounted, via a one way clutch means (13), as a free wheel, so that said first driving wheel means (1) is slightly axially moveable relative to said input shaft

₃₅ (10) along said threaded portion, and that a second axially moveable and freely rotatable driving wheel means (2) is mounted on said input shaft (10) for releasable engaging as a coupling means (17), the ring wheel (8) fixed to said input shaft (10), and that a third driving wheel means (23) is provided on the output shaft (21), said third driving wheel means (23) being constantly in mesh with said first driving wheel means (1), and that a fourth driving wheel means (24) is fixed to said output shaft (21) and is constantly in mesh with said second driving means (2), and means (7) pressing said first driving wheel means (1) axially toward and into engagement with said second driving wheel means

(2).

3.

An automatic transmission as defined in claims 1-2, c h a r a c t e r i z e d i n that at least one correspond¬ ing transmission (15') is connected in series so as to provide further transmission steps.

4.

An automatic transmission as defined in claims 1-3, c h a r a c t e r i z e d i n that the driving wheel means are gears, and are preferably helical gears.

5.

An automatic transmission as defined in claims 1-4, c h a r a c t e r i z e d i n that the external and internal threaded portions of said input shaft (10) and said first driving gear (1) are of the Bendix-drive type.

6.

An automatic transmission as defined in claims 1-5, c h a r a c t e r i z e d i n that said means (7) pressing said first driving wheel means in an axial direction comprises a spring and a spring seat (6).

7.

An automatic transmission as defined in claim 6, c h a r a c t e r i z e d i n that the spring seat (6) is axially displaceable along said input shaft (10) and provides an adjusting means for the spring force against said first driving wheel means (1).

8.

An automatic transmission as defined in claims 1-7, c h a r a c t e r i z e d i n that said releasable coupling means (17) comprises an external and an internal cone which

TIE are associated with said second driving wheel means (2) and said ring wheel (8), respectively, or vice versa.

9.

An automatic transmission as defined in claims 1-7,

15 c h a r a c t e r i z e d i n that said releasable coupling means (17) comprises a multi-disc clutch (52).

10.

An automatic transmission as defined in claims 1-9, zα c h a r a c t e r i z e d i n that between the first pair of driving wheel means (1,3) and between the_ second pair of driving wheel means (2,4) intermediate or planetary wheels (38,39) are provided.

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